The present invention relates to methods and constructions for attaching cylinders to each other, more particularly to methods and constructions for attaching hollow cylinders at the ends of the cylinders wherein at least one cylinder is made of composite material.
Conventional approaches to attaching composite cylinders either to other composite cylinders or to metallic cylinders implement bonded/bolted-joint or bolted-joint attachment schemes. The most common conventional methodology for cylinder attachment utilizes a scarf joint.
A significant limitation of these conventional attachment schemes is that the joint is permanent. If disassembly is required, the material is necessarily destroyed. Additionally, the use of a fastener creates some problems for either the bonded/bolted-joint attachment scheme or the bolted-joint attachment scheme. The mechanical fastener typically requires machining of the composite, which removes part of the material. This creates a weak point in the material, a site for stress concentrations, and a site for water migration or penetration from outside to inside.
One described approach accomplishes attachment of a composite cylinder to an aluminum end frame through a double-tapered joint that is machined into the composite shell after cure. See Harruff, P., Tsuchiyama T., and Spicola, F. C., "Filament Wound Torpedo Hull Structures," Fabricating Composites '86 Proceedings, Society of Manufacturing Engineers, Sep. 8-11, 1986, Baltimore, Md., incorporated herein by reference, esp. page 3. Although in this case the joint was detachable, it was still of greater stiffness than the bulk material and hence vulnerable. The machining and adhesive were critical to the viability of the joint.
For the B-1B composite Rotary Launch Tube, The U.S. Air Force attached composite cylinders together by adhesively bonding the composite cylinder to an aluminum forging; this method utilized a scarf or single-tapered joint. The composite was mechanically fastened to the metal with Hi-Lok fasteners in addition to the adhesive. Although the joint was thus also mechanically attached, the composite material was drilled and hence still compromised. With the removal of material and cutting of the fibers, this site not only manifested potential for reduced mechanical properties but for vulnerability to damage initiation and propagation.